Question

Political revolutions involve broad changes and the replacement of the existing political system with something new.

Answer 1

Yes, this is true, and I find this to be a fitting definition of political revolutions - the answer is "yes"

let's take for example the fall of the Socialist/Communist regimes in Eastern Europe in the late 1980s. They were connected to the removal of the existing political system (socialism) and their replacement with a new regime -free market and capitaism